PROPERTIES OF WAVES 5.2 Source and Creator: Stephanie Carles

Waves Review: Turn and talk to your partner. What do waves transfer? What is the difference between longitudinal and transverse waves? What are the high and low points of a transverse wave called? What are the parts of a longitudinal wave where the particles are spread out and close together?

Which of these show ONE full wave? One wave has one crest and one trough

Wavelength What is length a measure of? So what do you think a wave length is? The distance between two waves WAVELENGTH

Which has a shorter wavelength?

Measuring Wavelength Does this tell us the distance between the two waves? Why not? You have to measure the distance between two comparable points! (crest to crest, trough to trough, etc.)

Try It Stretch the string out across the table. Creating two waves: one with a large wavelength and one with a smaller one. Which wave did you have to put more effort into creating? Waves with _________________ wavelength have more energy. a shorter

Amplitude The distance between the crest or trough and the wave’s resting position. Where’s the crest? Trough? Resting Position Trough Crest Amplitude

Which has a larger amplitude?

What does amplitude tell us about a wave? Which of these waves would cause more damage if it hit the shore? Which has the larger amplitude? Which wave has more energy? THAT’S AMPLITUDE!

Try It Stretch the string out across the table. Create two waves: one with a large amplitude and one with a smaller one. Which wave did you have to put more energy into to create? Waves with _________________ amplitude have more energy. a larger

We’ve been looking at transverse waves…What about longitudinal? We can relate all of the parts of a transverse wave to a longitudinal one!

We’ll start with wavelength… In a transverse wave: But there aren’t any crests or troughs in a longitudinal wave! WAVELENGTH

So we look at the compressions and rarefactions! Compressions = Crests Rarefactions = Troughs Now we can find the wavelength Compression to compression Rarefaction to rarefaction

Frequency If your friend comes over to your house “frequently”, it means they come over often. Can you take a guess as to what the “frequency” of a wave is? Frequency: the number of waves in a certain amount of time.

We need to know how many waves are being produced in 10 seconds. How can you find the frequency of this wave? Step 1: pick a point on the wave. Step 2: count the waves that pass that point in 10 seconds.

Which has a higher frequency?

Try It Stretch the string out across the table. Create two waves: one with a high frequency and one with a lower one. Try to keep the amplitudes the same in both waves. Which wave did you have to put more energy into to create? Waves with _________________ frequency have more energy. a higher

Waves Review: Turn and talk to your partner. What do waves transfer? What is the difference between longitudinal and transverse waves? What are the high and low points of a transverse wave called? What are the parts of a longitudinal wave where the particles are spread out and close together?

What is the unit for frequency? Frequency is measured in Hertz (Hz). If one full wave passes a point every second, it has a frequency of 1 Hz. 1 wave/1 sec= 1 Hz. What is the frequency if three waves pass a point every second? 3 waves/1 second= 3 Hz. What is the frequency if six waves pass a point every three seconds? 6 waves/3 seconds= 2 Hz.

Quickwrite- Ticket Out the Door Explain four ways in which waves can be measured.

Wave Speed There are two ways to calculate wave speed. Option 1: time how long a wave takes to get from point A to point B. A B

Option 2: Use the following formula Wave speed = wavelength x frequency Wavelength – 2 meters Frequency – 4 Hz. (4 waves pass every second) Wave Speed = 8 meters/second

Review Turn and talk to your partner: What measurement is related to the distance from one wave crest to the next wave crest?